1. Field of the Invention
The present invention relates to a display system for an aircraft, in particular for a military transport plane.
More particularly, it relates to a display system comprising a head-down viewing device which comprises a plurality of electronic screens, of head-down type, that is to say which are provided on the instrument panel of the aircraft, and which present specific displays relating to the flight of the aircraft. Such a head-down viewing device may comprise, like any head-down screen, for example, a display and control system of CDS type (“Control and Display System”), a system relating to electronic instruments of EIS type (“Electronic Instrument System”), and/or any other standard screen.
2. Background of the Related Art
On an airplane, such as a civil transport plane for example, the head-down viewing device also comprises at least one screen, for example a primary piloting screen of PFD (“Primary Flight Display”) type, which is intended to display primary piloting information for the aircraft, such as the speed, altitude, attitude and/or heading in particular. It is known that this primary piloting information represents the most important information for the actual piloting.
On the other hand, in numerous military planes, in particular new-generation military transport planes, this primary piloting information is displayed in particular (and generally exclusively) on a (head-up) display means of a head-up viewing device of HUD type (“Head-Up Display”), this being in particular so as to facilitate the piloting of the airplane. It is known that such a head-up viewing device presents the information to be viewed superimposed on the environment seen in front of the aircraft, on a head-up display means which is transparent. Generally, the various items of information are projected directly onto this head-up display means which may be brought into the pilot's field of vision.
Thus, the pilot is directly aware of the essential piloting information, without needing to lower his head. This affords valuable aid to piloting and makes it possible to increase flight safety.
However, when there is a fault with such a head-up viewing device or when the latter is deliberately deactivated, this essential information is no longer available to the pilot, and this could disturb him during piloting, in particular in flight phases that are difficult to carry out and require deep concentration, such as a low-altitude flight, an approach or a take off for example.